Various technical alternatives are used for storing excess electric current which accumulates, for example, during current generation by renewable energy sources or by power stations which are operated within the range of optimum efficiency, and for which there is temporarily no need on the grid. One of these alternatives is the rechargeable metal-air battery (rechargeable oxide battery, ROB). ROBs are generally operated at temperatures of between 600° C. and 900° C. In this case, oxygen which is supplied to a (positive) air electrode of the electrical cell is converted into oxygen ions, transported by a solid electrolyte and brought to the opposite negative electrode (discharge operation) or transported from the negative electrode via the solid electrolyte to the air side (charging operation). A reduction or oxidation reaction with a gaseous redox pair takes place at the negative electrode (depending on whether charging or discharging is taking place), wherein the oxygen which is absorbed or given off by the gaseous redox pair is transferred by diffusion by the components of the redox pair to a porous, i.e. gas-permeable and likewise oxidizable and reducible storage medium. Owing to the high temperatures required, for example, for the transport of oxygen in the ceramic electrolyte for this process, the material selection for the cell materials used and the design of the cell parts and the arrangement of the storage medium are very complex. In particular, the individual components suffer after several redox cycles which are operated at said operating temperatures. In addition, an increase in the storage density per storage cell or per volume unit of the energy store is always desired for efficient use.